U.S. patent number 6,401,365 [Application Number 09/802,004] was granted by the patent office on 2002-06-11 for athletic shoe midsole design and construction.
This patent grant is currently assigned to Mizuno Corporation. Invention is credited to Yasunori Kaneko, Takaya Kimura, Kenjiro Kita.
United States Patent |
6,401,365 |
Kita , et al. |
June 11, 2002 |
Athletic shoe midsole design and construction
Abstract
A midsole assembly for an athletic shoe comprising a midsole and
a corrugated sheet. The midsole is formed of soft elastic material.
The corrugated sheet is disposed in at least a heel portion of the
midsole. Either or both amplitude and wavelength of wave
configuration of said corrugated sheet are made different either or
both between a front end portion and back end portion, and between
an medial portion and lateral portion of said heel portion.
Inventors: |
Kita; Kenjiro (Osaka,
JP), Kaneko; Yasunori (Osaka, JP), Kimura;
Takaya (Osaka, JP) |
Assignee: |
Mizuno Corporation (Osaka,
JP)
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Family
ID: |
14685466 |
Appl.
No.: |
09/802,004 |
Filed: |
March 8, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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910794 |
Aug 13, 1997 |
6219939 |
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Foreign Application Priority Data
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Apr 18, 1997 [JP] |
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9-116376 |
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Current U.S.
Class: |
36/28; 36/103;
36/30R; 36/31; 36/37 |
Current CPC
Class: |
A43B
13/12 (20130101); A43B 13/18 (20130101) |
Current International
Class: |
A43B
13/02 (20060101); A43B 13/12 (20060101); A43B
13/18 (20060101); A43B 013/12 (); A43B
013/18 () |
Field of
Search: |
;36/27,28,3R,35R,25R,31,92,87,102,3A,36A,37,71,44 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2032760 |
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May 1980 |
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GB |
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90/06699 |
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Jun 1990 |
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WO |
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Primary Examiner: Stashick; Anthony
Attorney, Agent or Firm: Sidley Austin Brown & Wood
Abrams; Hugh A.
Parent Case Text
This application is a continuation of application Ser. No.
08/910,794, filed Aug. 13, 1997, now U.S. Pat. No. 6,219,939.
Claims
What is claimed is:
1. A midsole assembly for an athletic shoe comprising:
a midsole formed of soft elastic material; and
a corrugated sheet made of plastic material, said sheet being
disposed in a heel region of said midsole, said corrugated sheet
extending across the full width of said heel region, said heel
region having a substantially constant thickness, amplitude of wave
configuration of said corrugated sheet being made different between
a medial and a lateral portion of said heel region, said corrugated
sheet thereby providing a higher compression hardness or lower
cushioning properties in said lateral portion of greater amplitude
than said medial portion of smaller amplitude of said heel portion;
and,
wherein said corrugated sheet is comprised of fiber-reinforced
plastic.
2. The midsole assembly of claim 1, wherein fibers of said
fiber-reinforced plastic are aligned in one direction.
3. The midsole assembly of claim 2, wherein fibers of said
fiber-reinforced plastic are oriented to the direction coinciding
with the direction of ridges of said wave configuration.
4. The midsole assembly of claim 2, wherein fibers of said
fiber-reinforced plastic are oriented within .+-.30.degree. with
relation to the direction of ridges of said wave configuration.
5. The midsole assembly of claim 1, wherein fibers of said
fiber-reinforced plastic are woven by filling and warp, the modules
of elasticity of said filling being larger than or equal to that of
said warp.
6. The midsole assembly of claim 5, wherein said filling is
oriented to the direction coinciding with the direction of ridges
of said wave configuration.
7. The midsole assembly of claim 5, wherein said filing is oriented
within .+-.30.degree. with relation to the direction of ridges of
said wave configuration.
Description
BACKGROUND OF THE INVENTION
The present invention relates to an athletic shoe midsole design
and construction. More particularly, the invention relates to a
midsole assembly where there are provided a midsole formed of soft
elastic material and a corrugated sheet disposed in the
midsole.
The sole of an athletic shoe used in various sports is generally
comprised of a midsole and an outsole fitted under the midsole,
directly contacting the ground. The midsole is typically formed of
soft elastic material in order to ensure adequate cushioning.
Running stability as well as adequate cushioning is required in
athletic shoes. There is need to prevent shoes from being deformed
excessively in the lateral or transverse direction when contacting
the ground.
As shown in Japanese Utility Model Examined Publication No.
61-6804, the applicant of the present invention proposes a midsole
assembly having a corrugated sheet therein, which can prevent such
an excessive lateral deformation of shoes.
The midsole assembly shown in the above publication incorporates a
corrugated sheet in a heel portion of a midsole and it can produce
resistant force preventing the heel portion of a midsole from being
deformed laterally or transversely when a shoe contacts the ground.
Thus, the transverse deformation of the heel portion of a shoe is
prevented.
However, it depends on the kind of athletics or athletes whether an
athlete lands on the ground more frequently from the medial portion
or the lateral portion of the heel at the onset of landing. For
example, since tennis or basketball players move more often in the
transverse direction and the medial portions of their heels tend to
first contact the ground, the heels lean outwardly and so-called
supination often occurs. On the other hand, since runners or
joggers tend to land on the ground from the lateral portions of
their heels and the load moves toward the toes, the heels lean
inwardly and so-called pronation often occurs.
These pronation and supination are normal movements when an
athlete's foot comes in contact with the ground. But over-pronation
or over-supination may cause damages to the ankle, knee and hip of
an athlete.
In the conventional midsole design there is provided a corrugated
sheet having a constant wave configuration in both the transverse
direction and the longitudinal direction of the heel portion.
Therefore, the prior art midsole has a constant compressive
hardness throughout the midsole and as a result, it cannot control
effectively pronation and supination of the foot of an athlete
although controlling them is required according to the kind of
athletics.
Generally, by inserting a corrugated sheet the heel portion of a
midsole tends to be less deformed in the transverse direction. When
the corrugated sheet is formed from high elastic material the heel
portion of a midsole tends to be less deformed in the vertical
direction as well. Therefore, when a corrugated sheet has a
constant wave configuration the heel portion of a midsole where
adequate cushioning is required may show less cushioning properties
in contacting the ground.
On the other hand, good cushioning is indispensable requirements of
athletic shoes but too high cushioning may absorb an athletic power
such as propellant or jumping power of an athlete.
The object of the present invention is to provide a midsole
assembly for an athletic shoe which can prevent the over-pronation
and over-supination in landing by preventing the shoe from being
deformed in the transverse direction according to the kind of
athletics and can not only ensure adequate cushioning but also
prevent an athletic power from being lessened.
SUMMARY OF THE INVENTION
The present invention provides a midsole assembly for an athletic
shoe and its manufacturing process.
In one embodiment, a midsole assembly comprises a midsole and a
corrugated sheet disposed in at least a heel portion of the
midsole. The midsole is formed of soft elastic material. Either or
both amplitude and wavelength of wave configuration of the
corrugated sheet is made different either or both between a front
end portion and back end portion, and between a medial portion and
lateral portion of the heel portion.
A second embodiment provides a midsole assembly according to the
first embodiment, wherein hardness of the corrugated sheet is
higher than that of the midsole.
A third embodiment provides a midsole assembly according to the
first embodiment, wherein the corrugated sheet is comprised of
fiber-reinforced plastic.
A fourth embodiment provides a midsole assembly according to the
third embodiment, wherein the fibers of the fiber-reinforced
plastic are aligned in one direction.
A fifth embodiment provides a midsole assembly according to the
fourth embodiment, wherein the fibers of the fiber-reinforced
plastic are oriented to the direction coinciding with the direction
of ridges of the wave configuration.
A sixth embodiment provides a midsole assembly according to the
fourth embodiment, wherein the fibers of the fiber-reinforced
plastic are oriented within .+-.30.degree. relative to the
direction of ridges of the wave configuration.
A seventh embodiment provides a midsole assembly according to the
third embodiment, wherein the fibers of the fiber-reinforced
plastic are woven by filling and warp, the modulus of elasticity of
the filling being greater than or equal to that of the warp.
An eighth embodiment provides a midsole assembly according to the
seventh embodiment, wherein the filling being oriented to the
direction coinciding with the direction of ridges of the wave
configuration.
A ninth embodiment provides a midsole assembly according to the
seventh embodiment, wherein the filling being oriented within
.+-.30.degree. relative to the direction of ridges of the wave
configuration.
A tenth embodiment provides a midsole assembly according to the
first embodiment, wherein a plurality of ribs are provided on the
surface of the corrugated sheet, the ribs being oriented to the
direction coinciding with the direction of ridges of the wave
configuration.
An eleventh embodiment provides a midsole assembly according to the
first embodiment, wherein the corrugated sheet is comprised of a
first corrugated sheet and a second corrugated sheet, the first
corrugated sheet being formed of thermoplastic or thermosetting
resin, the circumferential end surface thereof being located inside
the side surface of the heel portion of a shoe, the second
corrugated sheet being formed of soft elastic material having
smaller modulus of elasticity than that of the first corrugated
sheet, the circumferential end surface thereof being located at
substantially the same position as the side surface of the heel
portion of a shoe.
In a twelfth embodiment, a midsole assembly comprises a midsole and
a corrugated sheet disposed in at least a heel portion of the
midsole. The midsole is formed of soft elastic material and has an
aperture in the heel central portion. Either or both amplitude and
wavelength of wave configuration of the corrugated sheet is made
different either or both between a front end portion and back end
portion, and between a medial portion and lateral portion of the
heel portion.
A thirteenth embodiment provides a midsole assembly according to
the twelfth embodiment, wherein hardness of the corrugated sheet is
higher than that of the midsole.
A fourteenth embodiment provides a midsole assembly according to
the twelfth embodiment, wherein the corrugated sheet is comprised
of fiber-reinforced plastic.
A fifteenth embodiment provides a midsole assembly according to the
fourteenth embodiment, wherein the fibers of the fiber-reinforced
plastic are aligned in one direction.
A sixteenth embodiment provides a midsole assembly according to the
fifteenth embodiment, wherein the fibers of the fiber-reinforced
plastic are oriented to the direction coinciding with the direction
of ridges of the wave configuration.
A seventeenth embodiment provides a midsole assembly according to
the fifteenth embodiment, wherein the fibers of the
fiber-reinforced plastic are oriented within .+-.30.degree.
relative to the direction of ridges of the wave configuration.
An eighteenth embodiment provides a midsole assembly according to
the fourteenth embodiment, wherein the fibers of the
fiber-reinforced plastic are woven by filling and warp, the modulus
of elasticity of the filling being greater than or equal to that of
the warp.
A nineteenth embodiment provides a midsole assembly according to
the eighteenth embodiment, wherein the filling being oriented to
the direction coinciding with the direction of ridges of the wave
configuration.
A twentieth embodiment provides a midsole assembly according to the
eighteenth embodiment, wherein the filling being oriented within
.+-.30.degree. relative to the direction of ridges of the wave
configuration.
A twenty-first embodiment provides a midsole assembly according to
the twelfth embodiment, wherein a plurality of ribs are provided on
the surface of the corrugated sheet, the ribs being oriented to the
direction coinciding with the direction of ridges of the wave
configuration.
A twenty-second embodiment provides a midsole assembly according to
the twelfth embodiment, wherein the corrugated sheet is comprised
of a first corrugated sheet and a second corrugated sheet, the
first corrugated sheet being formed of thermoplastic or
thermosetting resin, the circumferential end surface thereof being
located inside the side surface of the heel portion of a shoe, the
second corrugated sheet being formed of soft elastic material
having smaller modulus of elasticity than that of the first
corrugated sheet, the circumferential end surface thereof being
located at substantially the same position as the side surface of
the heel portion of a shoe.
In a twenty-third embodiment, there is provided a process for
forming a midsole assembly for an athletic shoe wherein a
corrugated sheet is disposed in at least a heel portion of a
midsole. In this embodiment, the process comprises the steps of
overlaying a first flat sheet on a second flat sheet, where the
first flat sheet is formed of thermoplastic or thermosetting resin
and the circumferential end surface thereof is located inside the
side surface of the heel portion of a shoe, and the second flat
sheet is formed of soft elastic material having smaller modulus of
elasticity than that of the first flat sheet and the
circumferential end surface thereof is located at substantially the
same position as the side surface of the heel portion; and forming
the first and second flat sheets into corrugated sheets by placing
the first and second flat sheets in a mold and thermoforming
them.
For a better understanding of these and other embodiments of the
invention, reference should be made to the following detailed
description taken in conjunction with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
For a more complete understanding of the invention, reference
should be made to the embodiments illustrated in greater detail in
the accompanying drawings and described below by way of examples of
the invention. In the drawings, which are not to scale:
FIG. 1 is a side view of an athletic shoe incorporating the present
invention midsole construction.
FIG. 2 is an exploded, perspective view of a portion of the midsole
construction of the present invention.
FIG. 3 is a perspective view of a portion of a corrugated sheet in
the midsole construction of the present invention.
FIG. 4 is a side sectional view of the corrugated sheet.
FIG. 5 is a graph showing the relations between moment of inertia
of area I, wavelength .lambda. and amplitude A of the corrugated
sheet.
FIG. 6 is a graph showing the relations between bending rigidity EI
and cushioning coefficient C of the midsole having a corrugated
sheet therein.
FIGS. 7-12 are schematics illustrating a forming process of the
midsole construction of the present invention.
FIGS. 13-19 are schematics illustrating the midsole construction of
the present invention. In each Figure, (a) is a top plan view of
the midsole construction of a left side shoe; (b) is an outside
side view thereof; (c) is an inside side view thereof.
FIG. 20 is a perspective view of a portion of a corrugated sheet in
the midsole construction of the another embodiment of the present
invention.
FIG. 21 is a schematic illustrating the midsole construction of the
alternative embodiment of the present invention. In the Figure, (a)
is a plantar view of the midsole construction of a left side shoe;
(b) is a sectional view taken along the line X--X.
FIG. 22 is a schematic illustrating maximum pressures by the
contour lines, forced against the sole of a human foot while his or
her running.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Turning now to the drawings, FIG. 1 illustrates an athletic shoe
incorporating a midsole construction of the present invention. The
sole of this athletic shoe 1 comprises a midsole 3, a corrugated
sheet 4 and an outsole 5 directly contacting the ground. The
midsole 3 is fitted to the bottom of uppers 2. The corrugated sheet
4 is disposed in the midsole 3. The outsole 5 is fitted to the
bottom of the midsole 3.
The midsole 3 is provided in order to absorb a shock load imparted
on the heel portion of the shoe 1 when landing on the ground. As
shown also in FIG. 2, the midsole 3 is comprised of an upper
midsole 3a and a lower midsole 3b which are respectively disposed
on the top and bottom surfaces of the corrugated sheet 4.
The midsole 3 is generally formed of soft elastic material having
good cushioning properties. Specifically, thermoplastic synthetic
resin foam such as ethylene-vinyl acetate copolymer (EVA),
thermosetting resin foam such as polyurethane (PU), or rubber
material foam such as butadiene or chloroprene rubber are used.
When the midsole construction of the present invention is applied
to a typical athletic shoe, foam having about 1-100 kg/cm.sup.2,
preferably about 10 kg/cm.sup.2, of the modulus of elasticity is
utilized as the foam for forming the midsole 3.
The corrugated sheet 4 is formed of thermoplastic resin such as
thermoplastic polyurethane (TPU) of comparatively rich elasticity,
polyamide elastomer (PAE), ABS resin and the like. Alternatively,
the corrugated sheet 4 is formed of thermosetting resin such as
epoxy resin, unsaturated polyester resin and the like.
For example, when the midsole construction of the present invention
is applied to a typical athletic shoe a thermoplastic polyurethane
sheet of about 1 mm thickness, having about 100-50000 kg/cm.sup.2,
preferably about 1000 kg/cm.sup.2, of the modulus of elasticity is
utilized as the corrugated sheet 4.
As described above, in the present invention midsole construction
the corrugated sheet 4 is interposed between the upper midsole 3a
and the lower midsole 3b, and the sheet 4 is integrated with the
midsole 3a and 3b.
In this midsole construction the pressure imparted from the upper
midsole 3a in landing is dispersed by the corrugated sheet 4 and
the pressured area of the lower midsole 3b becomes enlarged. As a
result, compressive hardness throughout the midsole construction is
made higher.
Generally, the compressive hardness is determined by bending
rigidity EI (E: Young's modulus, I: moment of inertia of area) of
the material forming the corrugated sheet 4.
Now, as shown in FIG. 3, take the coordinate system over the
corrugated sheet 4 and consider that the bending moment M around
the z-axis is imparted to the corrugated sheet 4.
Supposing the corrugated sheet 4 is formed by bending a sheet of t
in thickness into sine curved configuration of amplitude A and
wavelength .lambda., the vertical cross sectional view of the
corrugated sheet 4 is shown in FIG. 4. The wave configuration of
this cross section can be expressed by the following equation 1.
##EQU1##
When there is a relation of L=n.lambda. (L: the whole length of the
corrugated sheet 4, n: natural number), the neutral axis of this
section is y=0. The moment of inertia of area I of this section
with relation to the neutral axis can be expressed by the following
equation 2 when a minute area on the section is ds. ##EQU2##
The relations between wavelength .lambda., amplitude A and moment
of inertia of area I are shown in FIG. 5 as t=1 (mm), L=100 (mm).
As seen from FIG. 5, amplitude A solely contributes moment of
inertia of area I and wavelength .lambda. seldom does when
wavelength .lambda. exceeds a certain value.
When it is confirmed by the equation, the equation 2 would be as
follows in the case of .lambda.>>A. ##EQU3##
This equation 3 shows that moment of inertia of area I is
proportional to the square of amplitude A but wavelength .lambda.
does not influence moment of inertia of area I at all when
wavelength .lambda. is adequately large compared to amplitude
A.
On the other hand, the equation 2 would be as follows in the case
of A>>.lambda.. ##EQU4##
This equation 4 shows that moment of inertia of area I is
proportional to the cube of amplitude A and inversely proportional
to wavelength .lambda. when wavelength .lambda. is adequately small
compared to amplitude A.
In fact, influence of amplitude A and wavelength .lambda. upon
moment of inertia of area I would be the intermediate between the
above equations 3 and 4. In either case, influence of amplitude A
upon moment of inertia of area I is extremely large compared to
wavelength .lambda..
Next, FIG. 6 shows the relation between bending rigidity EI and
cushioning properties. In FIG. 6, C axis of ordinate represents
cushioning coefficient. The cushioning coefficient C represents
cushioning properties of the midsole 3 having the corrugated sheet
4 therein. The coefficient C is a comparative value when
compressive deformation of a midsole 3 without a corrugated sheet,
to which a predetermined load is applied, is the basic value of
100. As seen from FIG. 6, as the bending rigidity EI becomes
larger, the cushioning coefficient C becomes smaller and cushioning
properties become poor, but stability is improved.
Therefore, where stability on landing is required in the midsole 3
the compressive hardness should be increased by enlarging the
moment of inertia of area I and thus the bending rigidity EI
through enlarging the amplitude A and decreasing the wavelength
.lambda.. On the contrary, where cushioning properties on landing
are required in the midsole 3 the compressive hardness should be
decreased by decreasing the moment of inertia of area I and thus
the bending rigidity EI through decreasing the amplitude A and
enlarging the wavelength .lambda..
In this way, by properly adjusting amplitude A and wavelength
.lambda., bending rigidity EI can be adjusted, and thus compressive
hardness of the whole midsole construction will come to be
adjusted.
Alternatively, since compressive hardness of the whole midsole
construction is generally determined by the amplitude A rather than
the wavelength .lambda. of the corrugated sheet 4, regulation of
compressive hardness may be made solely by the amplitude A, and
regulation of the bending deformation properties of the midsole
construction (i.e. how the midsole construction deforms in landing
along the ridge line or ravine line of the wave configuration of
the corrugated sheet) may be made by the wavelength .lambda..
Necessary procedures for forming the above midsole construction are
as follows. The values in the following description are merely
examples and the present invention is not limited to these
examples.
Method 1
First, a flat sheet 3b' (see FIG. 7) of about 10-20 mm thickness,
made of soft elastic material, is cut along the circumference of
the heel of an athletic shoe. This flat sheet 3b' will constitute
the lower midsole 3b after forming process has been completed.
Then, a flat sheet 4' (see FIG. 7) of about 0.5-2 mm thickness,
made of thermoplastic or thermosetting resin, is cut into a
slightly smaller circumferential configuration than that of the
heel. This flat sheet 4' will constitute the substantial (or
functional) corrugated sheet 4 after forming. A flat sheet 4" (see
FIG. 7) of about 0.5-2 mm thickness, made of soft elastic material,
is cut along the circumference of the heel. This flat sheet 4" will
constitute the seeming (or appearing) corrugated sheet 4 after
forming.
In addition, the flat sheet 4" has preferably different color or
design from that of the flat sheet 3b' such that the
circumferential end surface of the flat sheet 4" can be
distinguished from that of the lower midsole 3b after forming
process has been completed.
Second, the flat sheets 4' and 4" are bonded onto the upper surface
of the flat sheet 3b' (see FIG. 7) and then, as shown in FIG. 8,
these flat sheets 3b', 4' and 4" are inserted into a cavity 10a of
a mold 10. In FIG. 7 the flat sheets 4' and 4" are placed on the
flat sheet 3b' sequentially, but the flat sheets 4' and 4" may be
adversely placed. In addition, in FIGS. 7 and 8 (also in FIGS. 9 to
12), each thickness of the flat sheets 4' and 4" is shown
exaggeratingly for the purpose of clarification.
The outer measurement d1 of the flat sheets 3b' and 4" is larger
than the inner measurement D of the cavity 10a. However, since the
flat sheets 3b' and 4" formed of soft elastic material have smaller
modulus of elasticity and are easy to be deformed, these flat
sheets 3b' and 4" are easy to be inserted into the cavity 10a.
On the other hand, the flat sheet 4' formed of thermoplastic or
thermosetting resin has larger modulus of elasticity and is hard to
be deformed. However, since the outer measurement d2 of the flat
sheet 4' is slightly smaller than the inner measurement D of the
cavity 10a, the flat sheet 4' is also easy to be inserted into the
cavity 10a.
Next, as shown in FIGS. 8 and 9, the mold 12 having a corrugated
bottom surface 12a is inserted into the cavity 10a of the mold 10,
and then pressed and heated. When the mold 12 has returned after
this thermoforming, as shown in FIG. 10, the lower midsole 3b
having a corrugated upper surface is obtained and also, the
corrugated sheet 4 formed of the flat sheets 4' and 4" is
obtained.
In addition, a flat sheet of about 10-20 mm thickness, made of soft
elastic material, is cut along the circumference of the heel of an
athletic shoe, as in the case of forming the lower midsole 3b.
Then, by inserting this cut sheet into a mold set, one of which has
a corrugated surface, pressing and heating it, the upper midsole 3a
having a flat top surface and a corrugated bottom surface is formed
through thermoforming. The maximum thickness of the upper midsole
3a after forming is set about 10-15 mm.
Then, by bonding the corrugated surface of the upper midsole 3a
onto the corrugated sheet 4 on the lower midsole 3b and integrating
them, the midsole construction of the present invention is
completed (see FIGS. 11 and 12).
Before thermoforming the lower midsole 3b and the corrugated sheet
4, as abovementioned, the circumferential end surface of the flat
sheet 4' is reced ed inwardly from the circumferential end surfaces
of the flat sheets 3b' and 4". Therefore, after thermoforming, the
circumferential end surface of the flat sheet 4' constituting the
substantial corrugated sheet 4 is buried inside the circumferential
end surfaces of the lower midsole 3b and flat sheet 4", and hard to
be distinguished from outside.
However, after forming, the circumferential end surface of the flat
sheet 4" contacting tightly with the flat sheet 4' is placed at the
same position as the side surface of the heel, and besides, the
flat sheet 4" has a different color or design from that of the
lower midsole 3b. Thus, the consumers and users of shoes can
distinguish the corrugated sheet by the existence of the sheet 4"
and as a result, aesthetic impression of shoes will be
improved.
In FIGS. 7-12, the corrugated sheet 4 is comprised of the flat
sheet 4' formed of thermoplastic or thermosetting resin and the
flat sheet 4" formed of soft elastic material. However, the
corrugated sheet 4 may be comprised solely of the flat sheet
4'.
In this case, by enlarging the outer measurement of the flat sheet
4', the circumferential end surface of the formed flat sheet 4' or
the corrugated sheet 4 should be preferably seen from outside.
However, since the flat sheet 4' has larger modulus of elasticity
and is hard to deform, the outer circumference of the enlarged flat
sheet 4' cannot enter the cavity of a mold and as a result, burrs
will occur around the outer circumference of the formed flat sheet
4'. Therefore, in this case, removal procedures of the burrs are
required.
Method 2
In the above method 1 there is shown a method wherein after bonding
the flat sheet constituting the corrugated sheet 4 onto the upper
surface of the lower midsole 3b the flat sheet and the upper
surface of the lower midsole 3b are formed into corrugated
configuration. But the present invention is not limited to this
method.
After forming the flat sheet and the upper surface of the lower
midsole 3b into corrugated configuration respectively and
separately, the corrugated sheet 4 may be interposed between the
lower corrugated surface of the upper midsole 3a and the upper
corrugated surface of the lower midsole 3b, and the sheet 4 may be
bonded between the midsoles 3a and 3b.
In this case, a flat sheet of about 10-20 mm thickness, formed of
soft elastic material, is cut along the circumferential
configuration of the heel.
Then, by inserting this cut flat sheet into a mold set, one of
which has a corrugated surface, and pressing and heating it, the
upper midsole 3a having a generally flat upper surface and a
corrugated bottom surface is formed through thermoforming. The
maximum thickness of the formed upper midsole 3a is set about 5-7
mm.
Similarly, a flat sheet of about 10-20 mm thickness, formed of soft
elastic material, is cut along the circumferential configuration of
the heel. Then, by inserting this cut flat sheet into a mold set,
one of which has a corrugated surface, and pressing and heating it,
the lower midsole 3b having a generally flat bottom surface and a
corrugated upper surface is formed through thermoforming. The
maximum thickness of the formed lower midsole 3b is set about 10-15
mm.
On the other hand, the corrugated sheet 4 may be formed through
either thermoforming or injection molding. In the case of
thermoforming, by inserting such a laminate of the flat sheets 4'
and 4" (or only the flat sheet 4') as was explained in the method 1
into a mold set, both of which have corrugated surfaces, and
pressing and heating it, the corrugated sheet 4 is obtained. In the
case of injection molding, by introducing the molten thermoplastic
resin into the injection mold having a corrugated surface, the
corrugated sheet 4 is obtained.
Then, by interposing the corrugated sheet 4 between the corrugated
surface on the bottom side of the upper midsole 3a and the
corrugated surface on the top side of the lower midsole 3b,
contacting the corrugated sheet 4 with both of the corrugated
surfaces of the upper and lower midsoles 3a, 3b, and integrating
them together, the midsole construction is obtained.
Method 3
The method 3 is entirely different from the abovementioned methods
1 and 2.
First, the corrugated sheet 4 is formed by thermoforming or
injection molding and the formed corrugated sheet 4 is placed in a
mold. Then, premixed polyurethane foam material is introduced into
the mold and foamed in it. Thus, the upper midsole 3a and lower
midsole 3b are formed integral with the upper and lower surfaces of
the corrugated sheet 4 and the midsole construction is
completed.
In the midsole construction formed by the abovementioned processes,
a shoe sole is constituted by bonding the outsole 5 on the bottom
surface of the lower midsole 3b. The outsole 5 is mainly comprised
of solid rubber and its landing surface has a plurality of slip
preventive grooves or projections.
In addition, a shank member made of hard rigid resin or metal may
be installed on the medial and lateral portions of the midfoot
portion (or the arch portion) of the midsole construction in order
to increase rigidity. Additionally, a member such as a stabilizer
and the like may be provided between the upper midsole 3a and the
vamp 2 so as to improve the stability of the heel portion.
Referring to FIGS. 13-22, there are shown various kinds of midsole
constructions of the present invention.
In the embodiment shown in FIG. 13, the following relation exists
between the amplitudes A1 and A2.
A1: the amplitude at the heel front end portion of the wave
configuration of the corrugated sheet 4;
A2: the amplitude at the heel back end portion of the wave
configuration of the corrugated sheet 4.
That is to say, in this case, since the amplitude of the wave
configuration of the corrugated sheet 4 is smaller at the back end
side of the heel portion and greater at the front end side of the
heel portion, adequate cushioning of the midsole 3 is sustained at
the back end side heel portion of the smaller amplitude and
compressive hardness of the midsole 3 is made higher at the front
en d side heel portion of the greater amplitude. As a result, in
the athletics where athletes land more frequently at the back end
side of their heel portions, shock load in landing can be
effectively eased at the heel back end side portion and cushioning
properties can be ensured, and besides, the heel portions of the
midsoles can be prevented from being deformed transversely after
landing.
In addition, after landing, when the load moves toward the heel
front end side portion of higher compressive hardness, the
excessive sinking of the heel portion can be restrained, and thus,
as the athletes move on to the next movements, loss in the athletic
power can be decreased.
In the embodiment shown in FIG. 14, the following relation exists
between the amplitudes Ai and Ao.
Ai: the amplitude at the heel medial portion of the wave
configuration of the corrugated sheet 4;
Ao: the amplitude at the heel lateral portion of the wave
configuration of the corrugated sheet 4.
That is to say, in this case, since the amplitude of the wave
configuration of the corrugated sheet 4 is greater at the medial
side of the heel portion and smaller at the lateral side of the
heel portion, adequate cushioning of the midsole 3 is sustained at
the heel lateral portion of the smaller amplitude and compressive
hardness of the midsole 3 is made higher at the heel medial portion
of the greater amplitude. As a result, in the athletics where
athletes land more frequently at the lateral side of their heel
portions, shock load in landing can be effectively eased at the
heel lateral portions and cushioning properties can be ensured.
Moreover, when a foot is about to lean toward the heel medial
portion after landing, the foot can be supported by the heel medial
portion of the midsole and the heel portion of the midsole can be
prevented from being deformed transversely after landing.
In addition, after landing, when the heel of a foot has pronated,
the excessive sinking of the heel portion of a foot toward the
midsole medial portion can be prevented by the heel medial portion
of higher compressive hardness, and thus, over-pronation can be
prevented.
In the embodiment shown in FIG. 15, the following relation exists
between the amplitudes Ai, Ao as in the embodiment shown in FIG.
14.
Moreover, the following relation also exists between the
wavelengths .lambda.i and .lambda.o.
.lambda.i: the wavelength at the heel medial portion of wave
configuration of the corrugated sheet 4;
.lambda.o: the wavelength at the heel lateral portion of wave
configuration of the corrugated sheet 4.
In this embodiment, as in the embodiment shown in FIG. 14, since
the amplitude of wave configuration of the corrugated sheet 4 is
greater at the heel medial portion and smaller at the heel lateral
portion, in the athletics where athletes land more frequently at
the lateral side of their heel portions, cushioning can be ensured
and the heel portion of the midsole can be prevented from being
deformed transversely after landing.
Moreover, in this case, the wavelength of wave configuration of the
corrugated sheet 4 is greater at the heel medial portion and
smaller at the heel lateral portion. In the athletics where
athletes land more frequently at their heel lateral portions, when
they land on the ground from the heel portions toward the toe
portions of the shoes in sequence, the load path (or the load
carrying path) can nearly coincide with the direction perpendicular
to each ridge line of wave configuration. The direction of each
ridge line or generating line is shown by x in FIG. 3 and the
direction perpendicular to each ridge line or director line is
shown by z in FIG. 3. In this case, the midsole 3 deforms along the
ridge lines or ravine lines of wave configuration when landing.
As a result, the transverse deformation and the over-pronation at
the heel portion can be securely prevented and the larger contact
area can be secured when landing. Thus, grip properties and wear
resistant properties can be improved.
When this midsole construction is applied to a typical athletic
shoe, each measurement is set as follows:
e.g.) Ai=6 (mm), Ao=3.25 (mm), .lambda.i=40 (mm), .lambda.o=25
mm
In the embodiment shown in FIG. 16, the following relation exists
between the amplitudes Ai, Ao as in the embodiment shown in FIG.
14.
Moreover, the following relation also exists between the
wavelengths .lambda.i and .lambda.o, different from the embodiment
in FIG. 15.
In this case, the wavelength of wave configuration of the
corrugated sheet 4 is greater at the heel lateral portion and
smaller at the heel medial portion. In the athletics where athletes
land more frequently at their heel medial portions, when they land
on the ground from the heel portions toward the toe portions of the
shoes in sequence, the load path can nearly coincide with the
direction perpendicular to each ridge line of wave
configuration.
As a result, the transverse deformation and the over-pronation at
the heel portion can be securely prevented and the larger contact
area can be secured when landing. Thus, grip properties and wear
resistant properties can be improved.
In the embodiment shown in FIG. 17, the following relation exists
between the amplitudes Ai and Ao, different from the embodiment in
FIG. 14.
That is to say, in this case, since the amplitude of wave
configuration of the corrugated sheet 4 is greater at the lateral
side of the heel portion and smaller at the medial of the heel
portion, adequate cushioning of the midsole 3 is sustained at the
heel medial portion of the smaller amplitude and compressive
hardness of the midsole 3 is made higher at the heel lateral
portion of the greater amplitude.
As a result, in the athletics where athletes land more frequently
at the their heel medial portions, shock load in landing can be
effectively eased at the heel medial portions and cushioning can be
ensured. Moreover, when a foot is about to lean toward the heel
lateral portion after landing the foot can be supported by the heel
lateral portion of the midsole and the heel portion of the midsole
can be prevented from being deformed transversely after
landing.
In addition, after landing, when the heel of a foot has supinated,
excessive sinking of the heel portion of a foot can be restrained
by the heel lateral portion of higher compressive hardness, and
over-supination can be prevented.
In the embodiment shown in FIG. 18, the following relation exists
between the amplitudes Ai, Ao as in the embodiment shown in FIG.
17.
Moreover, the following relation also exists between the
wavelengths .lambda.i and .lambda.o.
In this case, since the amplitude of wave configuration of the
corrugated sheet 4 is greater at the lateral side of the heel
portion and smaller at the medial side of the heel portion, as in
the embodiment shown in FIG. 17, in the athletics where athletes
land more frequently at the medial side of their heel portions,
cushioning can be ensured and the heel portion of the midsole can
be prevented from being deformed transversely after landing.
Furthermore, in this embodiment, the wavelength of wave
configuration of the corrugated sheet 4 is greater at the heel
lateral portion and smaller at the heel medial portion. Therefore,
in the athletics where athletes land more frequently at their heel
medial portions, when they land on the ground from the heel
portions toward the toe portions of the shoes in sequence, the load
path can nearly coincide with the direction perpendicular to each
ridge line of wave configuration. That is to say, the midsole 3
deforms along the ridge lines or ravine lines of wave configuration
when landing.
As a result, the transverse deformation and the over-supination at
the heel portion can be securely prevented and the larger contact
area can be secured when landing. Thus, grip properties and wear
resistant properties can be improved.
In the embodiment shown in FIG. 19, the following relation exists
between the amplitudes Ai, Ao as in the embodiment in FIG. 17.
Moreover, the following relation also exists between the
wavelengths .lambda.i and .lambda.o, different from the embodiment
in FIG. 18.
That is to say, in this embodiment, the wavelength of wave
configuration of the corrugated sheet 4 is greater at the heel
medial portion and smaller at the heel lateral portion. Therefore,
in the athletics where athletes land more frequently at their heel
lateral portions, when they land on the ground from the heel
portions toward the toe portions of the shoes in sequence, the load
path can nearly coincide with the direction perpendicular to each
ridge line of wave configuration. As a result, the transverse
deformation and the over-supination at the heel portion can be
securely prevented and the larger contact area can be secured when
landing. Thus, grip properties and wear resistant properties can be
improved.
In another embodiment (not shown), the corrugated sheet 4 of each
of the abovementioned embodiments has a higher hardness than that
of the midsole 3. Generally, as shock load is repeatedly imparted
to the midsole 3 when landing, the corrugated sheet 4 repeats
deformation with the midsole 3. As a result, the midsole 3
gradually loses its elasticity and it becomes easy to be worn. On
the contrary, when hardness of the corrugated sheet 4 is set
higher, the midsole 3 becomes hard to be worn due to the
restorative properties of the corrugated sheet 4. As a result,
shock load in landing can be relieved during a prolonged use and
cushioning can be secured.
In further embodiment (not shown), the corrugated sheet 4 of each
of the abovementioned embodiments is formed of the fiber reinforced
plastic (FRP). Thus, the corrugated sheet 4 will have improved
elasticity and durability and be able to bear a prolonged use. The
fiber reinforced plastic (FRP) is comprised of reinforcement fiber
and matrix resin. Reinforcement fiber may be carbon fiber, aramid
fiber, glass fiber and the like. Matrix resin may be thermoplastic
or thermosetting resin.
In still further embodiment (not shown), each fiber of FRP in the
above embodiment is oriented to the direction coinciding with the
ridge direction of wave configuration of the corrugated sheet 4.
Thus, elasticity in the ridge direction can be selectively improved
without excessively increasing elasticity in the direction
perpendicular to the ridge line.
Preferably, FRP fiber is aligned in one direction. In addition, FRP
fiber is plain weave woven by a filling and warp. Preferably, the
modulus of elasticity of the filling is greater than or equal to
that of the warp and the filling is oriented to the direction
coinciding with the ridge direction of wave configuration of the
corrugated sheet 4.
Moreover, FRP fiber is aligned in one direction and the fiber is,
preferably, oriented to the direction within .+-.30.degree. with
relation to the ridge direction of wave configuration of the
corrugated sheet 4. In addition, preferably, the fiber is woven by
the filling and warp, and the modulus of elasticity of the filling
is greater than or equal to that of the warp, and the filling is
oriented to the direction within .+-.30.degree. with relation to
the ridge direction of the wave configuration of the corrugated
sheet 4.
Especially, when each ridge line direction is not respectively
parallel as in the embodiments shown in FIGS. 15 and 16, the
directions of aligned fibers and the filling should be oriented
coinciding with the ridge line direction running through the
general center line of the heel portion, and be oriented to the
direction within .+-.30.degree. with relation to the other ridge
line directions.
In the embodiment shown in FIG. 20, there are provided a plurality
of ribs 6 along the ridge lines on the surface of the corrugated
sheet 4. By adopting such a rib construction in the corrugated
sheet 4, elasticity in the ridge direction can be selectively
improved without excessively increasing elasticity in the direction
perpendicular to the ridge line direction.
In the embodiment shown in FIG. 21, there is provided an aperture
20 penetrating the outsole 5 and lower midsole 3b in the center
region of the heel portion of a shoe sole.
In addition, FIG. 22 shows the maximum pressures by contour lines,
forced upon the plantar of a foot during running or jogging. As
seen from FIG. 22, the maximum forces are imparted to the central
region of the heel portion. Therefore, adequate cushioning is
required in the central region of the heel portion.
As shown in FIG. 21, when there is provided an aperture 20 in the
center region of the heel portion, it will relatively decrease
compressive hardness of the midsole construction in the center
region by the compressive hardness taken by the lower midsole
3b.
As a result, adequate cushioning can be obtained in the center
region. Moreover, in this embodiment, since the corrugated sheet 4
of a moderate elasticity supports the pressure received by the heel
portion and disperses it in the lower midsole 3b and the outsole 5,
the heel portion will not sink excessively.
Especially, It is very effective to provide an aperture in the heel
portion of a shoe where its sole has a heel portion of an
independent structure or of a slip preventive construction such as
studs and the like because in this kind of sole landing pressure is
easy to concentrate on the heel portion, compared to the flat
sole.
In addition, some elderly people are attacked with pains caused by
the fact that fats in the heel portions grow thin and the calcaneus
spinae are pressed. The above aperture is also effective in easing
these pains.
Those skilled in the art to which the invention pertains may make
modifications and other embodiments employing the principles of
this invention without departing from its spirit or essential
characteristics particularly upon considering the foregoing
teachings. The described embodiments and examples are to be
considered in all respects only as illustrative and not
restrictive. The scope of the invention is, therefore, indicated by
the appended claims rather than by the foregoing description.
Consequently, while the invention has been described with reference
to particular embodiments and examples, modifications of structure,
sequence, materials and the like would be apparent to those skilled
in the art, yet still fall within the scope of the invention.
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